diff --git a/contracts-c/toolbox/guard.c b/contracts-c/toolbox/guard.c
new file mode 100644
index 0000000..a2ef865
--- /dev/null
+++ b/contracts-c/toolbox/guard.c
@@ -0,0 +1,57 @@
+
+#include <stdint.h>
+#include "hookapi.h"
+
+#define DONE(x)\
+    return accept(SBUF(x), __LINE__)
+
+#define NOPE(x)\
+    return rollback(SBUF(x), __LINE__)
+
+#define ASSERT(x)\
+{\
+    if (!(x))\
+        rollback(0,0,__LINE__);\
+}
+
+#define ACCID_SIZE 20U
+
+int64_t hook(uint32_t r)
+{
+    _g(1,1);
+
+    uint8_t hook_accid[32];
+    hook_account(hook_accid + 12, ACCID_SIZE);
+    
+    uint8_t otxn_accid[32];
+    otxn_field(otxn_accid + 12, ACCID_SIZE, sfAccount);
+
+    if (BUFFER_EQUAL_20(hook_accid + 12, otxn_accid + 12))
+        DONE("guard.c: passing outgoing txn");
+
+    ASSERT(otxn_slot(1) == 1);
+    ASSERT(slot_subfield(1, sfBlob, 2) == 2);
+    uint8_t buffer[2800];
+    ASSERT(slot(SBUF(buffer), 2) > 0);
+    uint16_t len = (uint16_t)buffer[0];
+    TRACEVAR(len);
+    uint8_t* ptr = buffer + 1;
+    if (len > 192)
+    {
+        len = 193 + ((len - 193) * 256) + ((uint16_t)(buffer[1]));
+        ptr++;
+    }
+
+    uint8_t* end = ptr + len;
+    int64_t count = 0;
+    while (ptr < end)
+    {
+        GUARD(100);
+        ASSERT(state_set(ptr + 1U + ACCID_SIZE, 8U, ptr + 1U, ACCID_SIZE) == 8U);
+        ptr += 1U + ACCID_SIZE + 8U;
+        count++;
+        TRACEVAR(count);
+    }
+    DONE("guard: Accounts Added.");
+    return 0;
+}
\ No newline at end of file
diff --git a/test/integration-c/hooks/toolbox/guard.test.ts b/test/integration-c/hooks/toolbox/guard.test.ts
new file mode 100644
index 0000000..8f6c83a
--- /dev/null
+++ b/test/integration-c/hooks/toolbox/guard.test.ts
@@ -0,0 +1,209 @@
+// xrpl
+import { Invoke, SetHookFlags, TransactionMetadata } from 'xahau'
+import {
+  // Testing
+  XrplIntegrationTestContext,
+  setupClient,
+  teardownClient,
+  serverUrl,
+  // Main
+  Xrpld,
+  SetHookParams,
+  ExecutionUtility,
+  createHookPayload,
+  setHooksV3,
+  clearAllHooksV3,
+} from '../../../../dist/npm/src'
+import { BaseModel, Metadata, UInt64, XRPAddress } from '@transia/binary-models'
+
+const accounts = [
+  'rNfd5LnXUkx1a6Jm6HyJhgYhxHxCxBQWpa',
+  'rhB9zpsW8puHN8UFLBrGzVWKPbokxREXq6',
+  'rEeqzxBFcoxhk3x91F4XUjm9y4c81KV8f7',
+  'rnmvzwjC1hKXpVL1yHEsHxywMdxvDu5X2H',
+  'rEj8GhozdUEzYFNyNmSpsX5gNUXH4aVmp2',
+  'rMijxTdkRSZYLzQn9ZXdg8rWMHbkQLGXPb',
+  'rEk782hC2xVeHfp61gtJxpMBGovGw81rV',
+  'rhiqgyXc7c9ypPYWDnuACFszddQMyiGckj',
+  'rNvXbJtCE2dcmTq4RB86idQwy9AFFrptp7',
+  'rn1rXYXDyVYfy8aVnVju54S6QnpzKhkFYG',
+  'r4fstovu3FELQEPF5oyTFdp7HLyKEo1FxW',
+  'rsYqdi6qmftywFYKgCkCVMRdggmR11FYvD',
+  'rJVCJMHkg32i1nbRtUvsVD2g2o911Uzb3z',
+  'rfDLm6MskDxNdUvHUeFf37vohGjTpe2SxV',
+  'rJMGRQc4aXZKF9zUErhQ43LRHwmWs1pKji',
+  'rpa7cwVmp7b52rQY9aEu5NdFULd8JCDoT9',
+  'rEP3hFWYPZthkPgCTyJmvcW8i5ae7CKvQp',
+  'r4j9iYVeey22d9ShvEusqqmtRApfrdyhjw',
+  'rhdvcvLVVycjheNHzyuMU7pxq4C8pGvaDX',
+  'rw7pSoMCRdJ7FhLpxBVzPEgSFHVFedE6qu',
+  'rxz364HGe9dBgLsNH8Dv2iDZdYpB4FEbX',
+  'rBSPqHUVPAMy47renKhxnwuRnJJF1F1s9B',
+  'rK42c8mWoAG1eEt4Cq5EeoWx1Poj3csk8P',
+  'rLVFuJvmvfZ6B63ss2f4EkdVnbaHNbZqVt',
+  'raZMnsD9uC6W4huUru9AhEM4vSVrS3nL3N',
+  'rUrxVLJyYVucJbohbXSD6dvVLPpobckD3A',
+  'rDPRQDymygF16RbUUnQbQfTsxA9yaRnTPC',
+  'rNLwcHGtJqTV9mxZw6YPotTDaj3TSFpMyn',
+  'rs1bvftRZXNUyqMcnHQn5CHeGcBkkz6ZuJ',
+  'rpcvftKzAD93S565KyXkZhWeGvs3EGxqth',
+  'rUPPQzb7etsN2ci9AcDSV36kskLoREd9us',
+  'rsRTbUX5NuBQv8obnJ29uGn5EWM24tpcgs',
+  'rMs6y7fakLAoHH2ffmoKiQ5fzwJ46cWiTM',
+  'r8CuT6d7vPamN8Q5o335dqtV4iQMud4e8',
+  'rJkF6e4Q2r9Rz4LkJgsnXwRBcfdKFbDBw6',
+  'rLMXFf5DdAU6pCmY2DBqj6iR47KM48kJEY',
+  'rKi5GjgurCUsTKXi9jkCUMmKr77kVR86Bm',
+  'rfFP2rnruzxowZ1jjBLYt4tvcohzWGZnaq',
+  'ra6YcM3Gjv45nztSPmjMAEefQ7pc9iTQrR',
+  'r4yFmirzVK2T98R1nmrzbX7ibziJkbUr5W',
+  'rHy2q6yBqaCqF5UmQJpfxHGSbcUvMNwj4G',
+  'rLM36BEnLTveS6eMPQCeQkbWtDLSC2qabH',
+  'rUpX4faHQHLaSHHcrRoQ6yzF7PfFy541Ji',
+  'rnD5zBnaEJc5YkiJB1SKSoZAzEWNp6UkUi',
+  'rGNqqFSoY4scNgh9cpVMawdtVamUoE6wxh',
+  'raSY1bQojAa7aXxwxd6PoaVCQ2Af5GgYPP',
+  'ran92PZiUoi7KKcQGc1cRVArawrNxfLAvd',
+  'rJtMfYVtWkPtdo4oMk2bcHRNfXNvsQf4uE',
+  'r9yz69n3MMsVt7rrLXzPHrD5LTLYTKZEf4',
+  'rFEorzuddGh7LPLCmobKE7EZXtGAJiT2A',
+  'rgop5VC9WGqLDmbU7h4CKSTeeEgTWQtrm',
+  'raZADqo65xKwfxZ61r77wwQEhuabqNDXix',
+  'rfVvPDrnAM19qzwEi7rJ8rHVsy614mvbLC',
+  'rE78YZuZ1LQfmTDtH72EW8bkn6xcTZczm9',
+  'rwEhiTvnW4CvLTtXkLt3y5RBgaBFvYsAVy',
+  'rGEwQ2K1L1NfdSEMXGkzy3bjaJVpgRkfgo',
+  'rUnaXMjUjPFh39kz58Q4F2HjuwVQxU2VuL',
+  'rKtZakSPiTguz89ychnVXemmYg8MzTfNn',
+  'rGopy4kMxZmUVmxzq3wJrRYb1Se6FtMLra',
+  'rn57fpmQiXC8KfBzW6iKszdBE2CchbcFgT',
+  'rKv6jPuHFiRdBHFL67cdc5noAaV8ycidpg',
+  'rKyTKttkBKSsALxCjivwS4sVndfq3xVh6k',
+  'rpyHRU3xSuPbJV6yVzxMgAPtrkPVBcLLbV',
+  'rL9U6iDn1Twg4VdT95J9vcZgdTk6HD5Bfx',
+  'rhowGD9QAnAJ5P9tGLVSNBWoPKdqdUKjHM',
+  'ra3j6M92VWgngy5SmJiuJMtakhMNew8P9K',
+  'rNSv8i8tnonexDMJbJaimuwMQGBzWJ2pDe',
+  'rpBPzzDpPnfiBCm8nt3SePaqy8CYpxWGS3',
+  'ramR4MUkzkg4HavFDS7qm1ZtSUUFyC5uDn',
+  'rMZyy7PSdk5B9ee4uGJcETGGsa9aQqcv8g',
+  'rM5wCXfwv8fzrDhLgH7yzRKoU5jRNKm1uS',
+  'rw16K7PVWt8s9CUaAMUby8tFNP6YTqa91k',
+  'rnwV3nTJU6ph2wKJHiAjXC5vXJ1eDyv4CR',
+  'rfn3pat4uCCfAsxGnzGbC6YkDDH3RQqzjz',
+  'rUn2nvVCCMVicrNcPcof1GwtfzbH3H97Gy',
+  'r9E5rWZ6T64xa5CPMEGw1F51mGEvcs3kAV',
+  'rLQHBo1NqhageUpMTfxCRdCXNNPAXKcCdG',
+  'rfQyBY8DFJ2qDhQPBVvikK2aef8uAQHPbV',
+  'r3CFk7paqsivHPXhfgrwj181YELWqyoJbL',
+  'rLJqP5wQtLNC6xWCGqZCpqcFYKko4DaixM',
+  'rsVy8DyjJzLB6byugTvJJdGk9L2qNXzdje',
+  'rK58F1WFaFKYy3ukguYLFemWCUDGzr3mdN',
+  'rw7wPnBQAoriHhS2uMfrfN3WsLW6ui5eJW',
+  'rhgnMUuXBJA7rK87uKJ2h26mzZ1i2QKwzz',
+  'rB9DMLytaBiVqyRFHZ2zVFE7wMoACK73x4',
+  'rMkhVhbxwa4ooTPSrAR8ebk3L5tjLWETC2',
+  'rN95xyS993LBqrkdtN9D8Vg64yYNuKCDcH',
+  'rKm8YH2FNZP2DQFG2wVWMJJ5ra5m2hZ8iD',
+  'rsiEZ631z44aWXKVoNxBAMY8UnRgXTKK1C',
+  'rUKJLetNjUmbaw7QUCWp3GGnCemxyTTGBr',
+  'r3d6Wr5YwYdAHwtRWoWFR3UAdn26drD1Mv',
+  'rpqCgmXGo65wfmmbEPbyCA6cFLBxy6W95m',
+  'rfYSktU5U1g5aefuEscbp8ccN34yzuxtap',
+  'rpJkKDZrEyCNUDGmVhs7aad3pxeQfMTktF',
+  'rsofdAGcktk91UK15vnuv5EHEcKsYqnDWV',
+  'rfncB4A1xuUis35ivxCNopKMf49xZhDX7t',
+  'rDqBejAV7cxdjmho7SBUERLVLNHHPenRD9',
+  'rK78DnCXh5sdKNfDJffi1oVfN1LBRMRFSS',
+  'r9JKasMnRpKjBZfGzD9kpZd4iDC5q5rBTR',
+  'rUUxcgTktAJQdT1rhvET43D99JffgN3Qwg',
+]
+
+export class Account extends BaseModel {
+  account: XRPAddress
+  count: UInt64
+
+  // Total Bytes: 28
+  constructor(account: XRPAddress, count: UInt64) {
+    super()
+    this.account = account // 0: 20 bytes
+    this.count = count // 20: 8 bytes
+  }
+
+  getMetadata(): Metadata {
+    return [
+      { field: 'account', type: 'xrpAddress' },
+      { field: 'count', type: 'uint64', little: true },
+    ]
+  }
+
+  toJSON() {
+    return {
+      account: this.account,
+      count: this.count,
+    }
+  }
+}
+
+describe('guard', () => {
+  let testContext: XrplIntegrationTestContext
+
+  beforeAll(async () => {
+    testContext = await setupClient(serverUrl)
+    const hook = createHookPayload({
+      version: 0,
+      createFile: 'guard',
+      namespace: 'guard',
+      flags: SetHookFlags.hsfOverride,
+      hookOnArray: ['Invoke'],
+    })
+    await setHooksV3({
+      client: testContext.client,
+      wallet: testContext.hook1,
+      hooks: [{ Hook: hook }],
+    } as SetHookParams)
+  })
+  afterAll(async () => {
+    await clearAllHooksV3({
+      client: testContext.client,
+      wallet: testContext.hook1,
+    } as SetHookParams)
+    await teardownClient(testContext)
+  })
+
+  it('guard hook', async () => {
+    // INVOKE IN
+    const aliceWallet = testContext.alice
+    const hookWallet = testContext.hook1
+
+    const whitelist: Account[] = []
+    for (let i = 0; i < accounts.length; ++i) {
+      whitelist.push(new Account(accounts[i], 1n))
+    }
+
+    let blob = ''
+    for (let i = 0; i < whitelist.length; ++i) {
+      const entry = whitelist[i]
+      blob += '00'
+      blob += entry.encode()
+    }
+
+    const builtTx: Invoke = {
+      TransactionType: 'Invoke',
+      Account: aliceWallet.classicAddress,
+      Destination: hookWallet.classicAddress,
+      Blob: blob,
+    }
+    const result = await Xrpld.submit(testContext.client, {
+      wallet: aliceWallet,
+      tx: builtTx,
+    })
+    const hookExecutions = await ExecutionUtility.getHookExecutionsFromMeta(
+      testContext.client,
+      result.meta as TransactionMetadata
+    )
+    expect(hookExecutions.executions[0].HookReturnString).toMatch(
+      'guard: Finished.'
+    )
+  })
+})